1. Field of the Invention
The present invention relates in general to an apparatus for controlling an automotive vehicle, more specifically, a vehicle control apparatus for controlling an engine, an automatic transmission and other devices of the vehicle. More particularly, the present invention is concerned with means for preventing an interference between running stability control means and manual transmission shifting control means.
2. Discussion of the Related Art
An automotive vehicle may fall in an unstable running condition, in particular, an unstable turning condition, with the lateral road gripping capacity of a wheel tire being exceeded during turning of the vehicle on a road surface having a relatively low friction coefficient, or at a relatively high speed, or to clear an obstacle, for example. The unstable running condition may be an oversteering or understeering tendency of the vehicle. The oversteering tendency is caused when the road gripping force of the rear wheels is considerably smaller than that of the front wheels, resulting in an excessively larger turning angle of the vehicle than the steering angle, and leading to a spinning tendency of the vehicle. On the other hand, the understeering tendency is caused when the road gripping force of the front wheels is considerably smaller than that of the rear wheels, resulting in a considerably smaller turning angle of the vehicle than the steering angle.
To cope with such running instability of the vehicle, there has been proposed running stability control means in the form of a turning stability control apparatus for stabilizing the vehicle turning behavior, such as a vehicle stability control system (VSC system) as disclosed in JP-A-4-266538. Such a turning stability control apparatus is activated when the vehicle turning condition is unstable, namely, when an oversteering or understeering tendency of the vehicle is detected. Described in detail, the apparatus is adapted to reduce the engine output and at the same time apply a braking force to an appropriate one or ones of the front and rear wheels, for producing a moment that reduces the oversteering or understeering tendency of the vehicle, thereby to stabilize the turning behavior of the vehicle.
The turning stability control apparatus may be further adapted to maintain the automatic transmission in the presently established position or shift up or down the automatic transmission, so as to improve the turning stability of the vehicle. The automotive vehicle equipped with the turning stability control apparatus may also be equipped with manual shifting control means which is adapted to shift the automatic transmission in response to an operation of a manual shifting device while a manual shift mode is selected. This type of vehicle may suffer from some drawbacks due to interferences or inadequate coordination between an operation of the turning stability control apparatus and an operation of the manual shifting control means, in relation to the shifting of the automatic transmission.
For instance, a drawback may arise if the automatic transmission is commanded by the manual shifting control means to shift the automatic transmission by manipulation of the manual shifting device in the manual shift mode while the automatic transmission is commanded by the turning stability control apparatus to maintain the presently established position for improving the turning stability of the vehicle. In this case, the automatic transmission may be shifted according to the command generated by the manual shifting control means, contrary to the command generated by the turning stability control apparatus to hold the automatic transmission in the presently established position.
The manual shifting means may be adapted such that the number of the selectable forward-drive operating positions of the automatic transmission which can be established for forward running of the vehicle can be changed by operation of the manual shifting device in the manual shift mode. Generally, the shift lever has two or more forward-drive positions such as xe2x80x9cDxe2x80x9d, xe2x80x9c3xe2x80x9d and xe2x80x9c2xe2x80x9d, and the hydraulic control device for the automatic transmission has range positions corresponding to the forward-drive positions of the shift lever. As the shift lever is operated from the position xe2x80x9cDxe2x80x9d to the position xe2x80x9c3xe2x80x9d and then to the position xe2x80x9c2xe2x80x9d, the number of the selectable forward-drive operating positions of the automatic transmission is reduced, for example, from xe2x80x9c4xe2x80x9d to xe2x80x9c3xe2x80x9d and from xe2x80x9c3xe2x80x9d to xe2x80x9c2xe2x80x9d. When the manual shifting device is operated, the range position of the hydraulic control device is electrically changed, and the number of the forward-drive operating positions of the automatic transmission is changed. If the manual shifting device is operated to change the number of the selectable forward-drive operating positions of the automatic transmission from xe2x80x9c4xe2x80x9d to xe2x80x9c3xe2x80x9d, for instance, the automatic transmission may be automatically shifted down from a fourth-speed position to a third-speed position, for example, as in the case where the shift lever is operated from the position xe2x80x9cDxe2x80x9d to the position xe2x80x9c3xe2x80x9d. Thus, the manual shifting device may be used to indirectly shift down or up the automatic transmission without operating the shift lever, by electrically changing the range position of the hydraulic control device. In this case, too, the vehicle control apparatus suffers from the drawback as described above with respect to the manual shifting means adapted to directly shift the automatic transmission.
It is therefore an object of the present invention to provide an apparatus for controlling an automotive vehicle, which apparatus ameliorates the conventionally encountered drawbacks due to an interference or inadequate coordination between the operation of the running stability control means and the manual shifting control means.
The above object may be achieved according to the principle of this invention, which provides an apparatus for controlling an automotive vehicle having an engine and an automatic transmission having a plurality of hydraulically operated frictional coupling devices, the apparatus comprising: (a) running stability control means operated upon reduction of stability of running of the vehicle below a predetermined threshold, for controlling at least one of an output of the engine, a braking force applied to the vehicle and an established position of the automatic transmission, so as to improve the stability of running of the vehicle; (b) manual shifting control means responsive to an operation of a manual shifting device, for shifting the automatic transmission; (c) running stability control detecting means for detecting an operation of the running stability control means; and (d) manual shifting control inhibiting means, operable upon detection of the operation of the running stability control means by the running stability control detecting means, for inhibiting an operation of the manual shifting control means while the running stability control means is operated to control said automatic transmission.
In the vehicle control apparatus of the present invention constructed as described above, the manual shifting control inhibiting means is operated upon detection by the running stability control detecting means of the operation of the running stability control means, to inhibit the operation of the manual shifting control means while the running stability control means is operated to control the automatic transmission. This arrangement prevents the conventionally encountered drawbacks due to interferences between the operation of the running stability control means and the operation of the manual shifting control means, in relation to the control of the automatic transmission. If, for example, the running stability control means generates a transmission hold command for holding the automatic transmission in the presently established position while the manual shifting device generates a manual shifting command to shift up or down the automatic transmission, the manual shifting control inhibiting means inhibits the operation of the manual shifting control means according to the manual shifting command, so that the automatic transmission is held in the presently established position according to the transmission hold command generated by the turning stability control means. Therefore, the running stability of the vehicle is not deteriorated by the shift-u or shift-down action of the automatic transmission according to the manual shifting command.
In one preferred form of the present invention, the apparatus further comprises: shift control means connected to the running stability control means and the manual shifting control means, for controlling the automatic transmission, the shift control means having an automatic shift mode in which the automatic transmission is automatically shifted depending upon a running condition of the vehicle, and a manual shift mode in which the manual shifting device is operable; and shift mode determining means for determining whether the shift control means is placed in the automatic shift mode or in the manual shift mode. In this form of the invention, the manual shifting control means commands the shift control means to shift the automatic transmission according to a manual shifting command generated by the manual shifting device when the shift mode determining means determines that the shift control means is placed in the manual shift mode, and the manual shifting control inhibiting means inhibiting the operation of the manual shifting control means according to the manual shifting command while the running stability control means is operated to control the automatic transmission.
In another preferred form of the invention, the apparatus further comprises: hydraulic control device for controlling the plurality of hydraulically operated frictional coupling devices, the hydraulic control device having a plurality of range positions which are selectively established and in which the automatic transmission have respective different numbers of forward-drive positions that can be established; shift control means connected to the the hydraulic control device, the running stability control means, the manual shifting control means, for controlling the frictional coupling devices of the automatic transmission, the shift control means having an automatic shift mode in which the automatic transmission is automatically shifted depending upon a running condition of the vehicle, and a manual shift mode in which the manual shifting device is operable; and shift mode determining means for determining whether the shift control means is placed in the automatic shift mode or in the manual shift mode. In this form of the invention, the manual shifting control means commands the shift control means to select one of the plurality of range positions of the hydraulic control device according to a manual shifting command generated by the manual shifting device when the shift mode determining means determines that the shift control means is placed in the manual shift mode, and the manual shifting control inhibiting means inhibiting the operation of the manual shifting control means according to the manual shifting command while the running stability control means is operated to control the automatic transmission.
In the above preferred form of the invention, the hydraulic control device may have: a first range position in which the automatic transmission can be shifted to any one of four forward-drive positions thereof consisting of a first-speed, a second-speed, a third-speed and a fourth-speed position; a second range position in which the automatic transmission can be shifted to any one of the first-speed, second-speed and third-speed positions but cannot be shifted to the fourth-speed position which is the highest speed position of all the four forward-drive positions; and a third range position in which the automatic transmission can be shifted to either one of the first-speed and second-speed positions but cannot be shifted to the third-speed and fourth-speed positions. If the manual shifting device is operated in the manual shift mode to generate a manual shifting command for controlling the hydraulic control device to newly establish the second range position while the first range position is established, the shift control means shifts down the automatic transmission from the fourth-speed position to the third-speed position if the automatic transmission is placed in the fourth-speed position when the manual shifting command is generated. Thus, the shift control means may shift the automatic transmission according to the manual shifting command generated by the manual shifting device in the manual shift mode for changing the range position of the hydraulic control device.
In a further preferred form of the invention, the manual shifting control device is operated to generate a manual shifting command for shifting the automatic transmission in the manual shift mode, and the running stability control means generates a stability control command for controlling the automatic transmission for improving the stability of running of the vehicle, and wherein the manual shifting control inhibiting means cancelling the manual shifting command to thereby inhibit the operation of the manual shifting control means while the stability control command is generated by the running stability control means. In this form of the invention, the manual shifting control means cancels or invalidates the manual shifting command which is generated by the manual shifting device. Thus, the manual shifting control inhibiting means gives priority to the running stability control operation by the running stability control means, to the manual shifting action of the automatic transmission under the control of the manual shifting control means according to the manual shifting command. Since the manual shifting command is cancelled and is not executed even after the shifting or holding of the automatic transmission according to the stability control command or even after the termination of the operation of the running stability control means.
In a still further preferred form of this invention, the apparatus further comprises transmission holding means operable when the running stability control detecting means detects that the operation of the running stability control means is terminated. This transmission holding means is adapted to hold the automatic transmission in a position thereof which is established upon termination of the operation of the running stability control means. In this form of the invention, the automatic transmission is held in the last established position until the manual shifting control means is operated according to a manual shifting command subsequently generated by the manual shifting device. Accordingly, the transmission holding means is effective to prevent an unnecessary shifting action of the automatic transmission immediately after the termination of the running stability control operation by the running stability control means.
In a yet further preferred form of the invention, the manual shifting control device is operated to generate a manual shifting command for shifting the automatic transmission in the manual shift mode, and the running stability control means generates a stability control shifting command for shifting the automatic transmission for improving the stability of running of the vehicle. In this form of the invention, the manual shifting control inhibiting means is adapted to cancel the manual shifting command generated by the manual shifting device if a shifting direction in which the automatic transmission is to be shifted according to the manual shifting command is the same as a shifting direction in which the automatic transmission is to be shifted according to the stability control shifting command generated by the running stability control means. Further, the manual shifting control inhibiting means permits the automatic transmission to be shifted according to the stability control shifting command, if the shifting direction according to the manual shifting command is the same as the shifting direction according to the stability control shifting command.
In still another preferred form of the invention, the manual shifting control device is operated to generate a manual shifting command for shifting the automatic transmission in the manual shift mode, and the running stability control means generates a stability control shifting command for shifting the automatic transmission for improving the stability of running of the vehicle, as in the above form of the invention. In this form of the invention, the manual shifting control inhibiting means permits the automatic transmission to be shifted according to the stability control shifting command generated by the running stability control means, if a shifting direction in which the automatic transmission is to be shifted according to the stability control shifting command is opposite to a shifting direction in which the automatic transmission is to be shifted according to the manual shifting command. However, the manual shifting control inhibiting means is adapted to hold the manual shifting command effective so that the automatic transmission is shifted according to the manual shifting command after the operation of the running stability control means. In this arrangement, the manual shifting command is not cancelled or invalidated by the manual shifting control inhibiting means, but is held effective so that the automatic transmission is shifted according to this manual shifting command after the shifting action of the automatic transmission according to the stability control shifting command or after the operation of the running stability control means.